The invention relates to a device for controlling the air supply to the inlet manifold of a combustion engine at a point located downstream of the throttle valve of the carburetor.
A combustion engine, particularly a gasoline engine used in a motor car frequently operates under conditions in which an excessive quantity of fuel is supplied for the required operation of the engine, which involves an excessively high fuel consumption and/or polution of the air.
If, for example, the number of revolutions of the engine in accelerating the vehicle is raised to about 3000 rev./min. and the clutch is subsequently loosened for changing over to a higher gear, the throttle is closed and the subatmospheric pressure in the inlet branch pipe downstream of the throttle generally attains a value which even exceeds that at a standstill of the rotating engine. Then a great pressure difference is created across the stationary fuel supply device, which thus delivers an unnecessarily large quantity of fuel. A fairly large portion of this fuel will leave the engine without being burnt and thus contribute to pronounced pollution of the air or this fuel is at least partly deposited in the inlet manifold and is again carried along at the subsequent opening of the throttle and hence at an increase in the quantity of air flowing through the inlet manifold, the fuel thus leaving the engine again without being combusted. Under these and similar conditions it is desirable to supply additional air downstream of the throttle in order to act upon the pressure difference across the throttle so that on the one hand undesirable and unnecessary supply of fuel is avoided at the instants when no power is required from the engine and on the other hand the ratio of air and fuel flows, is acted upon to effect a reduction of the fuel consumption of the engine and reduce air pollution.
According to the invention this can be achieved by providing the device with a closing member included in an air supply channel, the displacement of said member being controlled by at least one electromagnet, the energization of which is controlled by means of at least one switch responding to pressure variations occurring in the inlet system of the engine.
By using at least one switch determining the energization of an electromagnet actuating the closing member, pressure variations occurring in the inlet system are prevented from directly acting upon the displacement of the closing member, since otherwise undesirable or inadequate displacements of the closing member might be involved.